Thermal barrier coating material and method for production thereof, gas turbine member using the thermal barrier coating material, and gas turbine

ABSTRACT

A thermal barrier coating material, containing a metal binding layer laminated on a base material and a ceramic layer laminated on the metal binding layer, the ceramic layer comprising partially stabilized ZrO 2  which is partially stabilized by additives of Dy 2 O 3  and Yb 2 O 3 .

TECHNICAL FIELD

The invention relates to a thermal barrier coating material, a method ofproduction thereof, and a gas turbine member and a gas turbine to whichthe thermal barrier coating material is applied, and relates to usefularts which are applicable, for example, to thermal barrier coatings forrotor blades and stator blades of industrial gas turbines as well as forcombustors and other parts used in high-temperature environments.

BACKGROUND ART

Since high-temperature parts, such as rotor blades and stator blades ofindustrial gas turbines, and flame tubes, tail pipes, and split rings ofcombustors, etc., are used in high-temperature environments, they aregenerally provided with a thermal barrier coating on the surface.

FIG. 11 is a sectional view of a conventional thermal barrier coating.

The conventional thermal barrier coating film is arranged by laminatinga metal binding layer 12 of MCrAlY alloy on a base material 11 of arotor blade or the like and then further laminating a ZrO₂(zirconia)-based ceramic layer 13, for example, a layer of a partiallystabilized ZrO₂ which is partially stabilized by the addition of Y₂O₃ ata proportion of 6 to 8 wt % (hereinafter referred to as “YSZ”) on themetal binding layer 12 as a topcoat. Herein, the M in MCrAlY representsa solitary element or a combination of two or more elements selectedfrom Ni, Co, Fe and the like.

However, for recent gas turbines the turbine entrance temperature hasbeen increasing and thus higher thermal barrier properties are beingdemanded of topcoats. Also, thermal stress due to the thermal expansiondifference between the metal base material 11 and the ZrO₂-based ceramiclayer increases as the turbine entrance temperature increases. Thisthermal stress causes peeling of the topcoat and leads to degradation ofthe durability of the thermal barrier coating film. Improvements arethus needed to prevent the peeling of the topcoat.

Attempts have been already made to produce a ZrO₂-based ceramic ofcolumnar crystal form by the application of an electron beam physicalvapor deposition in the process of laminating the topcoat ceramic layer13. Attempts have also been made to produce microcracks in the thicknessdirection of a ZrO₂-based ceramic while forming the ZrO₂-based ceramicby thermal spraying. According to these methods, the peeling of thetopcoat can be prevented since the thermal stress caused between thebase material 11 and the ceramic layer 13 is alleviated.

Also, a partially stabilized ZrO₂ which is partially stabilized byaddition of Dy₂O₃ in place of Y₂O₃ (hereinafter referred to as “DySZ”)is gathering attention as a ceramic material which is approximately 20%lower than YSZ in thermal conductivity.

DISCLOSURE OF THE INVENTION

However, since the application process for the electron beam physicalvapor deposition requires a large amount of time, application to alarge-scale gas turbine or the like is difficult in terms of cost. Sincethe thermal conductivity of the obtained film becomes approximately 30%greater than that of porous ceramic, the film thickness must be madelarge, thus presenting a further difficulty in use. As for the method oflaminating the ceramic layer while forming the microcracks by thermalspraying, the formation of the microcracks requires a dense ceramiclayer, leading to the problem that the topcoat is increased in thermalconductivity and thus lowered in thermal barrier property. Furthermore,the microcracks are frequently formed not only in the thicknessdirection but also in the layer direction, leading to the problem thatthe ceramic layer peels in layers.

Moreover, DySZ is approximately 10% lower in linear thermal expansioncoefficient than YSZ. Thus, when a topcoat of thermal barrier coatingfilm is formed of DySZ, though a higher thermal barrier property can beobtained in comparison to the case where YSZ is used, the peelingresistance may become lower.

Regarding use of stabilized zirconia as a material for thermal sprayingin an application of thermal barrier coating (TBC), there is a knownmethod wherein after electromelting zirconia and yttria powders at 2500°C. or higher, the ingot obtained is pulverized to a mean particlediameter of 40 to 80 μm to produce a powder of stabilized zirconia forthermal spraying. There is another method wherein zirconia and yttriapowders are mixed in a slurry form, formed into spherical grains using aspray dryer, and then heated to produce a powder stabilized zirconiapowder for thermal spraying. However, in these methods, the mixing ofzirconia and yttria is not uniform due to the diffusion rate of zirconiabeing slower and the like. Thus, it is difficult to produce completelystabilized zirconia. That is, whereas completely stabilized zirconiashould be tetragonal crystals, some monoclinic zirconia remains.Although the monoclinic zirconia undergoes a phase modification totetragonal crystals at 1000° C., thermal stress can arise in theinterior due to the difference in thermal expansion coefficients ofmonoclinic crystals and tetragonal crystals.

The present invention has been made in view of the above circumstancesand an object of the first aspect of the invention is to provide athermal barrier coating material, wherein a topcoat of the thermalbarrier coating material is a ceramic layer which is porous and hasmicrocracks that extend in a thickness direction, thereby providing botha high thermal barrier property and a high peeling resistance, and amethod of producing the thermal barrier coating material.

Another object of the first aspect of the invention is to provide a gasturbine member which is adequately durable even in the environments ofhigher temperature than those of conventional temperatures, by anapplication of the thermal barrier coating material which provides botha higher thermal barrier property and a higher peeling resistance.

An object of the second aspect of the invention is to provide a thermalbarrier coating material which provides both a higher thermal barrierproperty and a higher peeling resistance in comparison to the materialin which YSZ is used as a topcoat.

Another object of the second aspect of the invention is to provide a gasturbine member that is adequately durable even in the environments ofhigher temperature than those of conventional temperatures, by anapplication of the thermal barrier coating material which provides botha higher thermal barrier property and a higher peeling resistance incomparison to the material in which YSZ is used as a topcoat.

An object of the third aspect of the invention is to provide, as a TBCraw material for thermal spraying, a stabilized zirconia powder beinghigh in stability wherein particles of a rare earth oxide such as yttriaare mixed uniformly with zirconia particles.

In achieving the above objects, the present inventors considered thatthe topcoat of a porous ceramic is effective for securing a higherthermal barrier property. The present inventors also considered thatmicrocracks that extend in the thickness direction in the ceramic layerare effective for securing a higher peeling resistance. As a result ofdiligent research, they came to complete the first aspect of theinvention.

The present inventors also paid attention to partially stabilized ZrO₂which is partially stabilized by Yb₂O₃ (hereinafter referred to as“YbSZ”). Since YbSZ has a 10 to 20% greater linear expansion coefficientthan YSZ or DySZ, it presents the possibility of providing a higherpeeling resistance. That is, the present inventor considered that acomposite material of DySZ and YbSZ, DySZ being higher in thermalbarrier effect than YSZ and YbSZ being higher in peeling resistance thanYSZ, can be used effectively as a topcoat and came to complete thesecond aspect of the invention as a result of diligent research.

Furthermore, the present inventors paid attention to the specificsurface areas of zirconium and rare earth oxide powders to be combinedto form the TBC raw material for thermal spraying and came to completethe third aspect of the invention.

That is, the thermal barrier coating material of the first aspect of theinvention is characterized in that a metal binding layer is laminated ona base material, and a ceramic layer of partially stabilized ZrO₂ whichis porous and has microcracks that extend in the thickness direction, islaminated on the metal binding layer. According to the invention, theporosity of the porous portion of the ceramic layer may be in the rangeof 1% to 30%. The density of the porous portion may be in the range of 4g/mm³ to 6.5 g/mm³. The thermal conductivity of the ceramic layer may bein the range of 0.5 w/m·K to 5 w/m·K. The number of the microcracks perunit length (1 mm) of a section of the ceramic layer may be in the rangeof 1 to 10.

According to this thermal barrier coating material, since the topcoat isthe ceramic layer comprising the partially stabilized ZrO₂ which isporous and yet has microcracks that extend in the thickness direction, ahigh thermal barrier effect comparable to conventional porous materialscan be provided, while a high peeling resistance comparable to materialsobtained by the electron beam physical vapor deposition can be alsoprovided. The thermal barrier coating material, which can provide anadequate thermal barrier effect and durability even in the environmentsof higher temperatures than those of conventional temperatures, is thusprovided.

The method for producing the thermal barrier coating material of thefirst aspect of the invention comprises the steps of: laminating a metalbinding layer on a surface of a base material, laminating a ceramiclayer on a surface of the metal binding layer, and causing microcrackswhich extend in the thickness direction in the ceramic layer byirradiating a surface of the ceramic layer with a laser beam and therebyheating the surface of the ceramic layer while cooling a rear surface ofthe base material. According to the invention, the surface of theceramic layer may be irradiated with a laser beam with a diameter in therange of 10 mm to 40 mm. The surface of the ceramic layer may be heatedto a temperature in the range of 1000° C. to 1700° C. by irradiationwith the laser beam. Irradiation with the laser beam may be carried outfrom 5 to 1000 times with the proviso that neither phase modificationnor sintering of the partially stabilized ZrO₂ will occur.

In the production method, the ceramic layer is laminated so that theporosity may be in the range of 1% to 30% or the density may be in therange of 4 g/mm³ to 6.5 g/mm³. Or, the microcracks are caused so thatthe thermal conductivity may be in the range of 0.5 w/m·K to 5 w/m·K, orthe number of the microcracks per unit length (1 mm) of a section of theceramic layer may be in the range of 1 to 10.

According to the method for producing the thermal barrier coatingmaterial, since microcracks are caused in the ceramic layer by laserbeam irradiation after lamination of the ceramic layer, the thermalbarrier coating material can be formed extremely simply in a shortperiod of time and at low cost. This method may also be appliedselectively to only thermally severe parts of a gas turbine member andthe like.

The gas turbine member of the first aspect of the invention ischaracterized in being covered with a thermal barrier coating filmproduced by laminating a metal binding layer on a base material andlaminating a ceramic layer on the metal binding layer, the ceramic layercomprising a partially stabilized ZrO₂ which is porous and hasmicrocracks that extend in the thickness direction. According to theinvention, the porosity of the porous portion of the ceramic layer maybe in the range of 1% to 30%. The density may be in the range of 4 g/mm³to 6.5 g/mm³. The thermal conductivity of the ceramic layer may be inthe range of 0.5 w/m·K to 5 w/m·K. The number of the microcracks perunit length (1 mm) of a section of the ceramic layer may be in the rangeof 1 to 10.

According to this gas turbine member, since the topcoat of the thermalbarrier coating film is the ceramic layer comprising the partiallystabilized ZrO₂ which is porous and yet has microcracks that extend inthe thickness direction, and the gas turbine member is covered with thethermal barrier coating film, the gas turbine member provides anadequate thermal barrier effect and durability even in environments ofhigher temperature than those of conventional temperatures.

According to the first aspect of the invention, provided is the gasturbine which generates motive power by expanding, by means of statorand rotor blades of the turbine, a fluid that has been compressed by acompressor and then combusted by a combustor. The gas turbine ischaracterized in that either or both of the stator and rotor blades arecovered with a thermal barrier coating film, produced by laminating ametal binding layer on a base material of the blade and laminating aceramic layer on the metal binding layer, the ceramic layer comprisingpartially stabilized ZrO₂ which is porous and has microcracks thatextend in the thickness direction. The ceramic layer preferablysatisfies one or more of the following conditions (1) to (4):

(1) The porosity of the porous portion of the ceramic layer is in therange of 1% to 30%.

(2) The density of the porous portion of the ceramic layer is in therange of 4 g/mm³ to 6.5 g/mm³.

(3) The thermal conductivity of the ceramic layer is in the range of 0.5w/m·K to 5 w/m·K.

(4) The number of the microcracks per unit length (1 mm) of a section ofthe ceramic layer is in the range of 1 to 10.

According to the second aspect of the invention, the thermal barriercoating material is characterized in that a metal binding layer islaminated on a base material and a ceramic layer is laminated on themetal binding layer, the ceramic layer comprising partially stabilizedzirconia which is partially stabilized by the additives of Dy₂O₃ andYb₂O₃. According to the invention, the added proportion of the Dy₂O₃ maybe in the range of 0.01 wt % to 16.00 wt %, the added proportion of theYb₂O₃ may be in the range of 0.01 wt % to 17.00 wt %, the sum of theadded proportions of Dy₂O₃ and Yb₂O₃ may be in the range of 10 wt % to20 wt %, and the added proportion of ZrO₂ may be in the range of 80 wt %to 90 wt %. Moreover, the ceramic layer may be a film produced bythermal spraying of a ZrO₂—Dy₂O₃—Yb₂O₃ powder obtained by mixing ZrO₂,Dy₂O₃ and Yb₂O₃ powders and forming a solid solution of this mixture.

According to this thermal barrier coating material, since the topcoatcomprises a composite material of DySZ and YbSZ, DySZ being higher inthermal barrier effect than YSZ and YbSZ being higher in peelingresistance than YSZ, a thermal barrier effect and a peeling resistancewhich are higher in comparison to the prior art can be provided. Thethermal barrier coating material, which provides an adequate durabilityeven in environments of higher temperature than those of conventionaltemperatures, can thus be provided.

The gas turbine member according to the second aspect of the inventionis characterized by being covered with a thermal barrier coating filmwhich is produced by laminating a metal binding layer on a base materialand laminating a ceramic layer on the metal binding layer. The ceramiclayer comprises partially stabilized zirconia which is partiallystabilized by adding Dy₂O₃ and Yb₂O₃. According to the invention, theDy₂O₃ may be added in the range of 0.01 wt % to 16.00 wt %, the Yb₂O₃may be added in the range of 0.01 wt % to 17.00 wt %, the sum of theadded Dy₂O₃ and Yb₂O₃ may be in the range of 10 wt % to 20 wt %, and theZrO₂ may be added in the range of 80 wt % to 90 wt %. The ceramic layermay be a film produced by thermal spraying of a ZrO₂—Dy₂O₃—Yb₂O₃ powderproduced by mixing ZrO₂, Dy₂O₃ and Yb₂O₃ powders and forming a solidsolution of this mixture, or a film produced by the electron beamphysical vapor deposition. A vacuum heat treatment for realizing goodadhesion of the undercoat with the base material may be performed in thefinal step.

According to this gas turbine member, since the topcoat of the thermalbarrier coating film comprises a composite material of DySZ and YbSZ,DySZ being higher in thermal barrier effect than YSZ, and YbSZ beinghigher in peeling resistance than YSZ, and since the gas turbine memberis covered with the thermal barrier coating film, the gas turbine memberhaving an adequate durability even in environments of higher temperaturethan those of conventional temperatures can be provided.

Moreover, the second aspect of the invention provides the gas turbinewhich generates motive power by expanding, by means of stator and rotorblades of the turbine, a fluid which has been compressed by a compressorand then combusted by a combustor. The gas turbine is characterized inthat either or both of the stator and rotor blades are covered with athermal barrier coating film produced by laminating a metal bindinglayer on a base material of the blades and laminating a ceramic layer onthe metal binding layer. The ceramic layer comprises partiallystabilized ZrO₂ which is partially stabilized by adding Dy₂O₃ and Yb₂O₃.The gas turbine preferably satisfies one or two or more of the followingconditions (1) to (3):

(1) The added Dy₂O₃ is in the range of 0.01 wt % to 16.00 wt %, theadded Yb₂O₃ is in the range of 0.01 wt % to 17.00 wt %, the sum of theadded Dy₂O₃ and Yb₂O₃ is in the range of 10 wt % to 20 wt %, and theZrO₂ which is other than the stabilizers is added in the range of 80 wt% to 90 wt %.

(2) The ceramic layer is a film produced by thermal spraying of aZrO₂—Dy₂O₃—Yb₂O₃ powder produced by mixing ZrO₂, Dy₂O₃ and Yb₂O₃ powdersand forming a solid solution of this mixture.

(3) The ceramic layer is a film produced by the electron beam physicalvapor deposition of an ingot having a predetermined composition.

According to the third aspect of the invention, provided is the TBC rawmaterial for thermal spraying, prepared by adding a zirconia powder anda rare earth oxide powder, each powder having a specific surface area ofat least 10 m²/g powder. Also provided is the method of producing theTBC raw material for thermal spraying wherein a zirconia powder having aspecific surface area of at least 10 m²/g and a rare earth oxide powderhaving a specific surface area of at least 10 m²/g are mixed along witha suitable binder or dispersant to be made into a slurry, thengranulated to form the particles having an average particle diameter of10 to 100 μm, and then heated at 1300 to 1600° C. for 1 to 10 hours.Also provided is the gas turbine member which has been covered with thefilm obtained by thermal spraying of the TBC raw material for thermalspraying, and the gas turbine comprising this gas turbine member.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of the thermal barrier coating film accordingto the first aspect of the invention.

FIG. 2 is a flowchart of an example of the thermal barrier coating filmproduction procedure according to the invention.

FIG. 3 is a sectional view of the thermal barrier coating film at one ofthe stages in the production thereof according to the first aspect ofthe invention.

FIG. 4 is a sectional view of the thermal barrier coating film at one ofthe stages in the production thereof according to the first aspect ofthe invention.

FIG. 5 is a sectional view of the thermal barrier coating film at one ofthe stages in the production thereof according to the first aspect ofthe invention.

FIG. 6 is a sectional view of an example of the thermal barrier coatingfilm according to the second aspect of the invention.

FIG. 7 is a flowchart of an example of a procedure for producing aZrO₂—Dy₂O₃—Yb₂O₃ powder.

FIG. 8 is a sectional view of an example of the thermal barrier coatingfilm according to the third aspect of the invention.

FIG. 9 is a flowchart of an example of a procedure for producing aZrO₂—rare earth oxide powder.

FIG. 10 is a diagram, showing an outline of the combustion gas thermalcycle test in Examples and Comparative examples.

FIG. 11 is a sectional view of a conventional thermal barrier coatingfilm.

FIG. 12 is a perspective view of a gas turbine rotor blade to which thethermal barrier coating film of the invention is applied.

FIG. 13 is a perspective view of a gas turbine stator blade to which thethermal barrier coating film of the invention is applied.

FIG. 14 is a general arrangement diagram of a gas turbine to which thethermal barrier coating film of the invention is applied.

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of the thermal barrier coating according to the firstaspect of the invention will be explained.

FIG. 1 is a sectional view of the thermal barrier coating film to whichthe thermal barrier coating material according to the first aspect ofthe invention is applied.

The thermal barrier coating film has a structure wherein an MCrAlY alloylayer is laminated as a metal binding layer 22 of excellent corrosionresistance and oxidation resistance on a base material 21 such as arotor blade, and a ZrO₂-based ceramic layer 23, which is partiallystabilized by one or two selected from the group consisting of Y₂O₃,Dy₂O₃ and Yb₂O₃, is laminated further on the metal binding layer 22 as atopcoat. The ceramic layer 23 is porous and comprises microcracks 24which extend in the thickness direction.

The metal binding layer 22 has a role in lowering the difference ofthermal expansion coefficient between the base material 21 and theporous ZrO₂-based ceramic layer 23 and thereby relaxing thermal stressso that the ceramic layer 23 is prevented from peeling off from the basematerial 21. Herein, the M in the MCrAlY alloy represents a solitaryelement or a combination of two or more elements selected from Ni, Co,Fe and the like.

In the porous ZrO₂-based ceramic layer 23, the porosity of the porousportion is preferably in the range of 1% to 30%. This is because whenthe porosity is less than 1%, the thermal conductivity may besignificantly high so that the thermal barrier effect may be low. Whenthe porosity is greater than 30%, the mechanical strength of the ceramiclayer may degrade significantly so that the thermal cycle resistance maybe poor. The porosity can be measured by an image analysis of asectional microstructure.

Moreover, the density of the porous portion of the ceramic layer 23 ispreferably in the range of 4 g/mm³ to 6.5 g/mm³. This is because whenthe density is less than 4 g/mm³, the mechanical strength of the filmmay be low. When the density is more than 6.5 g/mm³, the film may bedense and large in thermal conductivity so that the film may be poor inthermal barrier property.

The thermal conductivity of the ceramic layer 23 is preferably in therange of 0.5 w/m·K to 5 w/m·K. This is because when the thermalconductivity is more than 5 w/m·K, the merit of a thermal barriercoating may be insufficient. When the thermal conductivity is less than0.5 w/m·K, a large number of pores have been introduced so that the filmmay be low in mechanical strength and poor in thermal cycle resistance.This thermal conductivity can be measured by a laser flash method, whichis generally used for this type of thermal conductivity measurement.

The number of microcracks 24 per unit length (1 mm) of a section ofceramic layer 23 is preferably in the range of 1 to 10. This is becausewhen there is less than 1 crack per 1 mm, the thermal stress due to thedifference of linear expansion coefficient may not be eased so that theadvantage over the prior art may not be significant. When there are morethan 10 microcracks per 1 mm, the microcracks tend to become mutuallyconnected so that the thermal cycle resistance may be poor. The numberof microcracks can be determined from a sectional microstructure bymeasuring the number of microcracks per unit length parallel to the basematerial.

The thickness of the ceramic layer 23 is preferably 0.05 mm to 1.5 mm.This is because when the film thickness is 0.05 mm or less, the thermalbarrier effect may be low. When the film thickness is 1.5 mm or more,the durability may be low.

The thickness of the metal binding layer may be any thickness at whichthe difference of thermal expansion coefficient between the basematerial 21 and the ZrO₂-based ceramic layer 23 can be lowered andthereby the thermal stress can be eased.

A method for producing the thermal barrier coating film to which thethermal barrier coating material of the invention is applied will beexplained.

FIG. 2 is a flowchart of an example of the procedure for producing thethermal barrier coating film according to the invention.

Each of FIGS. 3 to 5 is a sectional view of one of the stages for theprocess for producing this thermal barrier coating film.

First, the metal binding layer 22 is laminated on the surface of thebase material 21 (see step S1 and FIG. 3). Preferably, a low pressureplasma spraying or an electron beam physical vapor deposition may beused as the method for laminating the metal binding layer 22.Subsequently, the ceramic layer 23 comprising porous and partiallystabilized ZrO₂, is laminated, for example, by thermal spraying on thesurface of the metal binding layer 22 (see step S2 and FIG. 4). A vacuumheat treatment process may thereafter be performed to realize goodadhesion between the bond coat and the base material.

Then, as shown in FIG. 5, while cooling the rear surface 21 a of thebase material 21, the surface 23 a of the ceramic layer 23 is irradiatedwith a laser beam 25 so as to bring the surface temperature of theceramic layer 23 to preferably 1000° C. to 1700° C. (step S3). Thereasons for the preference of the temperature range are as follows. Whenthe temperature is less than 1000° C., the number of laser irradiationsmay be unduly increased in order to form longitudinal microcracks andthus is poor in terms of economy. When the temperature is more than1700° C., the ceramic layer may undergo a phase modification orsintering in a short period of time and transverse microcracks may bealso caused in addition to longitudinal microcracks.

Moreover, during the laser irradiation, the laser beam diameter may bepreferably adjusted to be in the range of 10 mm to 40 mm on the surfaceof ceramic layer 23. This is because when the laser beam diameter isless than 10 mm, it may take more time to scan the laser beam and thusbe poor in economy. When the beam diameter is more than 40 mm, an undulyuneven temperature distribution in the laser spot may arise so that itmay be difficult to control the forms and the number of microcracks. Thelaser source may include a carbon dioxide gas laser.

The number of irradiations of the laser beam 25 may be preferably in therange of 5 times to 1000 times with the proviso that there is neither aphase modification nor sintering of the partially stabilized ZrO₂comprised by the ceramic layer 23. When it is less than 5 times, thelaser output may have to be increased so that the surface temperature ofthe ceramic layer may rise significantly. When it is more than 1000times, it may not be economical.

By irradiation of the laser beam 25, the microcracks 24 that extend inthe thickness direction are caused in the ceramic layer 23 as shown inFIG. 1 (step S4 of FIG. 2) so that the thermal barrier coating film isfinally attained.

The thermal barrier coating material having the above-describedstructure may be effectively applied to rotor and stator blades ofindustrial gas turbines and high temperature parts such as flame tubesand tail pipes of combustors. The thermal barrier coating material isnot limited to application to the industrial gas turbines but can beused as thermal barrier coating films for high temperature parts for theengines of automobiles, jets and the like.

An embodiment of the thermal barrier coating according to the secondaspect of the invention will be explained.

FIG. 6 is a sectional view of the thermal barrier coating film accordingto the invention.

The thermal barrier coating film has a structure wherein an MCrAlY alloylayer 122 is laminated as a metal binding layer of excellent corrosionresistance and oxidation resistance on a base material 121 such as arotor blade, and a partially stabilized ZrO₂ layer 123 which ispartially stabilized by Dy₂O₃ and Yb₂O₃ (hereinafter, referred to asZrO₂—(Dy₂O₃+Yb₂O₃)), is laminated further on the metal binding layer asa topcoat. Herein, the M in MCrAlY represents a solitary element or acombination of two or more elements selected from Ni, Co, Fe and thelike.

The MCrAlY alloy layer 122 has a role of lowering the difference ofthermal expansion coefficient between the base material 121 and theZrO₂—(Dy₂O₃+Yb₂O₃) layer 123 and thereby eases thermal stress so thatthe ZrO₂—(Dy₂O₃+Yb₂O₃) layer 123 is prevented from peeling off from thebase material 121. Here, the M in MCrAlY alloy layer 122 represents asolitary element or a combination of two or more selected from Ni, Co,Fe and the like. The MCrAlY alloy layer 122 may be laminated by a lowpressure plasma spraying or an electron beam physical vapor deposition.

In the ZrO₂—(Dy₂O₃+Yb₂O₃) layer 123, the preferable portions of additionof the respective components are as follows. The Dy₂O₃ may be added inthe range of 0.01 wt % to 16.00 wt %. The Yb₂O₃ may be added in therange of 0.01 wt % to 17.00 wt %. The sum of the added Dy₂O₃ and Yb₂O₃may be in the range of 10 wt % to 20 wt %. The ZrO₂ may be added in therange of 80 wt % to 90 wt %. The sum of the added Dy₂O₃ and Yb₂O₃ may bepreferable in the above-described ranges because when the sum is lessthan 10 wt %, the partial stabilization of the ZrO₂-based ceramic may beinadequate so that the stability at a high temperature in the long termmay be poor. When the sum is more than 20 wt %, the crystal structuremay change from a metastable tetragonal crystal to a structure that ismainly a cubic crystal so that the ceramic layer may be deterioratedsignificantly in strength and tenacity and lowered in the thermal cycleresistance. The thickness of ZrO₂—(Dy₂O₃+Yb₂O₃) layer 123 may bepreferably 0.1 mm to 1.5 mm. When the thickness is less than 0.1 mm, thethermal barrier effect may be inadequate. When the thickness is greaterthan 1.5 mm, the durability may be lowered significantly. The thicknessof the metal binding layer may be any thickness at which the merit oflowering the difference of thermal expansion coefficient between thebase material 121 and the ZrO₂—(Dy₂O₃+Yb₂O₃) layer 123 and therebyeasing thermal stress can be obtained. The thickness of the metalbinding layer may be preferably in the range of 0.03 to 11.0 mm.

The ZrO₂—(Dy₂O₃+Yb₂O₃) layer 123 may be laminated using aZrO₂—Dy₂O₃—Yb₂O₃ powder by an atmospheric pressure plasma spraying or anelectron beam physical vapor deposition. The ZrO₂—Dy₂O₃—Yb₂O₃ powderused for the atmospheric pressure plasma spraying is, for example,produced by the following procedure.

FIG. 7 is a flowchart, showing a procedure for producing aZrO₂—Dy₂O₃—Yb₂O₃ powder.

First, a ZrO₂ powder, a predetermined amount of Dy₂O₃ powder and apredetermined amount of Yb₂O₃ powder may be prepared (step S1), mixed ina ball mill along with a suitable binder or dispersant (step S2) so asto form a slurry (step S3). The mixture may be then dried by a spraydryer so as to be in the form of granulate (step S4) and thereafter madeinto a solid solution by a diffusion thermal process (step S5) so as toproduce a composite powder of ZrO₂—Dy₂O₃—Yb₂O₃ (step S6). By thermalspraying of this composite powder on the MCrAlY alloy layer 122, thethermal barrier coating film comprising the thermal barrier coatingmaterial of the invention may be obtained.

The binder to be used is not particularly limited and may includewater-based and resin-based binders. The dispersant to be used may beany dispersant by which the powders can be dispersed. The mixing meansis not limited to a ball mill and may include commonly used means formixing such an attritor. The granulation means is not limited to a spraydryer and may include commonly used means such as means for fusing or apulverizer. The ingot to be used for the electron beam physical vapordeposition may be prepared by sintering or electromelting andsolidifying a raw material having predetermined composition.

The thermal barrier coating material having said structure may beeffectively applied to rotor and stator blades of industrial gasturbines and high temperature parts such as flame tubes and tail pipesof combustors. The thermal barrier coating material is not limited tothe application of the industrial gas turbines but can be used asthermal barrier coating films for high temperature parts for the enginesof automobiles, jets and the like.

An embodiment of the TBC raw material for thermal spraying according tothe third aspect of the invention will be explained.

FIG. 8 is a sectional view of an example of the thermal barrier coatingfilm prepared by thermal spraying of the TBC raw material for thermalspraying according to the invention.

The thermal barrier coating film has a structure wherein, for example, aMCrAlY alloy layer 222 is laminated as a metal binding layer ofexcellent corrosion resistance and oxidation resistance on a basematerial 221 such as a rotor blade, and a partially stabilized ZrO₂which is partially stabilized by a rare earth oxide (hereinafterreferred to as ZrO₂-rare earth oxide) layer 223, is laminated further onthe metal binding layer as a topcoat. Here, the M in MCrAlY represents asolitary element or a combination of two or more elements selected fromNi, Co, Fe and the like.

The thickness of the ZrO₂-rare earth oxide layer 223 is preferably 0.1mm to 1.5 mm. This is because when the layer thickness is less than 0.1mm, the thermal barrier effect may be inadequate. When the layerthickness is greater than 1.5 mm, the durability may be loweredsignificantly. The thickness of the metal binding layer may be anythickness at which lowering the difference in thermal expansioncoefficients between the base material 221 and the ZrO₂-rare earth oxidelayer 223 and thereby relaxing thermal stress can be attained, and ispreferably in the range of 0.03 to 11.0 mm.

The MCrAlY alloy layer 222 has a role of lowering the difference inthermal expansion coefficients between the base material 221 and theZrO₂-rare earth oxide layer 223 and thereby relaxing thermal stress sothat the ZrO₂-rare earth oxide layer 223 is prevented from peeling offfrom the base material 221. Herein, the M in the MCrAlY alloy layer 222represents a solitary element or a combination of two or more elementsselected from Ni, Co, Fe and the like. The MCrAlY alloy layer 222 may belaminated by a low pressure plasma spraying or an electron beam physicalvapor deposition.

The ZrO₂-rare earth oxide layer 223 is produced by adding a zirconiapowder having a specific surface area of at least 10 m²/g to a rareearth oxide powder having a specific surface area of at least 10 m²/g.Herein, the specific surface area is measured by the BET method. Apowder having a specific surface area of at least 10 m²/g may be equalto a powder having a mean particle diameter of submicron. Althoughfurther investigation is required because the submicron powders havegreatly different features from conventional powders, it is consideredthat due to use of the zirconia powder of high specific surface area andthe rare earth oxide powder of high specific surface area, the particlesadhere together effectively and uniform mixing can be attained.

Zirconia powders having a specific surface area of at least 10 m²/g arecommercially available. Presently, zirconia powders having a specificsurface area as high as 50 m²/g are available and may be used favorably.

It is known that a rare earth oxide powder having a specific surfacearea of at least 10 m²/g can be obtained by thermal decomposition of acarbonate of a rare earth. Presently, rare earth oxide powders having aspecific surface area as high as 30 m²/g are available and may be usedfavorably. For example, thermal decomposition of a carbonate of a rareearth such as yttrium carbonate or dysprosium carbonate at 700 to 1000°C. produces a rare earth oxide powder. When the temperature is higherthan 1000° C., the particles may grow and the particle size may increaseso that the specific surface may decrease. When the temperature is lessthan 700° C., the decomposition of the carbonate may be inadequate.Although thermal decomposition of an oxalate of a rare earth is alsogenerally used as a method of producing a rare earth oxide, the thermaldecomposition of the oxalate yields only rare earth oxides having aspecific surface area of a few m²/g.

Examples of preferable rare earth oxides include yttria (Y₂O₃),dysprosia (Dy₂O₃), ytterbia (Yb₂O₃), neodymia (Nd₂O₃), samaria (Sm₂O₃),europia (Eu₂O₃), gadolinia (Gd₂O₃), erbia (Er₂O₃), lutetia (Lu₂O₃) andmay be used solitarily or as a mixture thereof. The more preferableexamples include yttria, dysprosia, and ytterbia.

As for the ZrO₂-rare earth oxide layer 223, the content of the rareearth oxide is preferably in the range of 3 to 8 mol % and the contentof ZrO₂ is preferably in the range of 92 to 97 mol %. This is because,within this composition range, the crystal structure is mainly ofstructure called a metastable tetragonal T′ phase, and this structurehas a high durability. When the rare earth oxide content is less than 3moles, monocrystals may be formed in terms of crystal structure and mayhave a volume change in a heating or cooling process, resulting inlowered durability. When the content is more than 8 mol %, the crystalstructure may become a cubic crystal and the durability may beinadequate.

The ZrO₂-rare earth oxide layer 223 is laminated by thermal spraying ofa ZrO₂-rare earth oxide powder. The thermal spraying method includescommonly used methods and is not particularly limited. Examples includeatmospheric pressure plasma spraying, ultrahigh-speed flame spraying andlow pressure plasma spraying. The ZrO₂-rare earth oxide powder used forthe thermal spraying may be, for example, produced by the followingprocedure.

FIG. 9 is a flowchart, showing an example of a procedure for producing aZrO₂-rare earth oxide powder.

First, a ZrO₂ powder and a rare earth oxide powder having predeterminedspecific surface areas, respectively, are prepared at a predeterminedratio (step S1), placed and mixed together with a suitable binder ordispersant in a ball mill or the like (step S2), and made into a slurry(step S3). The mixture is then granulated to particles having an averageparticle diameter of 10 to 100 μm by a spray dryer or the like (step S4)and then heated at 1300 to 1600° C. for 1 to 10 hours (step S5) toobtain a composite powder of ZrO₂-rare earth oxide (step S6). Thermalspraying of this composite powder onto the MCrAlY alloy layer 222produces the thermal barrier coating film of the invention to which theTBC raw material for thermal spraying has been applied.

The binder to be used is not particularly limited and may includewater-based and resin-based binders. The dispersant to be used may beany dispersant by which the powders can be dispersed. The mixing meansis not limited to a ball mill and may include an attritor and othernormally used means. The granulation means is not limited to a spraydryer and may include normally used means such as means for fusing or apulverizer.

The thermal barrier coating material with said structure may beeffectively applied to rotor and stator blades of industrial gasturbines and high temperature parts such as flame tubes and tail pipesof combustors. The thermal barrier coating material is not limited toapplication to industrial gas turbines but can be used as thermalbarrier coating films for high temperature parts for the engines ofautomobiles, jets and the like.

FIGS. 12 and 13 are perspective views of turbine blades to which thethermal barrier member described in the embodiment of the first, secondor third aspect of the invention is applicable.

The gas turbine rotor blade 4 in FIG. 12 is equipped with a tab tail 41which is fixed to a disk, a platform 42, a blade part 43 and the like.

The gas turbine stator blade 5 in FIG. 13 is equipped with an innershroud 51, outer shroud 52, blade part 53 and the like. The blade part53 comprises seal fin cooling holes 54, slit 55 and the like.

Both gas turbine rotor blade 4 and gas turbine stator blade 5 areapplicable to a gas turbine in FIG. 14.

The gas turbine in FIG. 14 will be explained briefly.

This gas turbine 6 is equipped with a compressor 61 and a turbine 62,which are directly connected to each other. The compressor 61 isarranged, for example, as an axial flow compressor and sucks in air or apredetermined gas as a working fluid from an inlet port and raises thepressure of this air or predetermined gas. A combustor 63 is connectedto the discharge port of this compressor 61, and the working fluid whichhas been discharged from compressor 61 is heated by combustor 63 to apredetermined turbine entrance temperature. The working fluid which hasbeen raised in temperature to the predetermined temperature is thensupplied to turbine 62. As shown in FIG. 14, several (four in theFigure) of the above-described gas turbine stator blades 5 are fixed tothe interior of the casing of turbine 62. Also, the above-described gasturbine rotor blades 4 are mounted to the main shaft 64 so that eachrotor blade 4 forms a single stage with each stator blade 5. One end ofthe main shaft 64 is connected to the rotating shaft 65 of thecompressor 61 and the other end is connected to the rotating shaft of angenerator (not shown).

According to such a structure, when a high-temperature and high-pressureworking fluid is supplied into the casing of the turbine 62 fromcombustor 63, the working fluid expands inside the casing to cause themain shaft 64 to rotate and thereby to drive the generator (not shown).That is, pressure is dropped by the respective stator blades 5 fixed tothe casing, and the kinetic energy thereby generated is converted torotational torque via the respective rotor blades 4 mounted to the mainshaft 64. The rotational torque generated is transmitted to the mainshaft 64 and the generator is thereby driven.

Typically, the material used in the gas turbine rotor blades is aheat-resistant alloy (for example, CM247LC which is an alloy materialsold by Canon Muskegon Corp.) and the material used in the gas turbinestator blades is likewise a heat-resistant alloy (for example, IN939which is an alloy material sold by Inco Corp.). That is, as thematerials for the turbine blades, heat-resistant alloys which can beemployed as the base materials of the thermal barrier members of theinvention are used. Thus, when a thermal barrier material of theinvention is coated onto a turbine blade, a turbine blade having a highthermal barrier effect and peeling resistance can be obtained.Consequently, it is applicable in environments higher in temperature,durability is improved and a long life is realized. Improvement of thegas turbine efficiency is also possible if the temperature of theworking fluid is increased.

According to said embodiment of the first aspect of the invention, sincethe topcoat is the ceramic layer 23 which comprises the partiallystabilized ZrO₂ which is porous and yet has the microcracks 24 thatextend in the thickness direction, a higher thermal barrier effect and ahigher peeling resistance than those of the prior art can be obtained.The thermal barrier coating material which is adequately durable even inthe environments of higher temperatures than those of conventionaltemperatures, can thus be provided.

Moreover, according to the embodiment of the first aspect of theinvention, since the microcracks 24 are formed in ceramic layer 23 byirradiation of the laser beam 25 after the lamination of the ceramiclayer 23, the thermal barrier coating material can be produced extremelysimply and at low cost. This method may also be applied selectively toonly the thermally severe parts of a gas turbine member and the like.

Moreover, covering high temperature parts for a gas turbine and the likewith the thermal barrier coating material can produce a gas turbinemember and like which are adequately durable even in the environments ofhigher temperature than those of conventional temperatures.

According to the embodiment of the second aspect of the invention, sincethe topcoat is a layer 123 of ZrO₂—(Dy₂O₃+Yb₂O₃) which is a compositematerial of DySZ and YbSZ, DySZ being higher in thermal barrier effectthan YSZ, and YbSZ being higher in peeling resistance than YSZ, a higherthermal barrier effect and a higher peeling resistance than those of theprior art can be obtained. Thus, the thermal barrier coating materialwhich is adequately durable even in the environments of highertemperature than those of conventional temperatures can be provided.

Moreover, covering high temperature parts for a gas turbine and the likewith this thermal barrier coating material can produce a gas turbinemember and the like which is adequately durable even in the environmentsof higher temperature than those of conventional temperatures.

According to the embodiment of the third aspect of the invention, sincethe topcoat is the ZrO₂-rare earth oxide layer 223 which is produced bythermal spraying of a TBC raw material for thermal spraying obtained byuniformly mixing zirconia having a specific surface area of at least 10m²/g, preferably in the range of 10 to 50 m²/g, with a rare earth oxidehaving a specific surface area of at least 10 m²/g, preferably in therange of 10 to 30 m²/g, a stabilized zirconia layer with higherstability than the prior art is obtained. The thermal barrier coatingmaterial which is adequately durable even in the environments of highertemperature than those of conventional temperatures can thus beprovided.

Moreover, covering high temperature parts for a gas turbine and the likewith this thermal barrier coating material can produce a gas turbinemember and the like which is adequately durable even in the environmentsof higher temperature than those of conventional temperature.

Examples and comparative examples will be described below to clarify thefeatures of the invention.

In the respective examples and comparative examples below, a Ni-basedalloy (Ni-16Cr-8.5Co-1.7Mo-2.6W-1.7Ta-0.9Nb-3.4Al-3.4Ti) was used as thebase material of the heat-resistant alloy. The base material was made 30mm square in size and 5 mm in thickness. The CoNiCrAlY(Co-32Ni-21Cr-8Al-0.5Y) was used as the metal binding layer.

EXAMPLES 1 TO 15

The sample Nos. 1 to 15 described below were prepared.

(Sample No. 1)

The surface of the base material was grid-blasted with Al₂O₃ particlesand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. A ceramic layer comprising porous andpartially stabilized ZrO₂, which had been partially stabilized by 8 wt %of Y₂O₃ as an additive, was then formed to a thickness of 0.5 mm byatmospheric pressure plasma spraying. Then, while cooling the rearsurface of the base material, the top surface of the ceramic layer wassubject to 30 seconds×100 times of irradiations of a laser beam from acarbon dioxide laser. Thus, the heat cycle was repeated. In thisprocess, the top surface of the ceramic layer was heated to a maximumtemperature of 1400° C. The irradiation area per spot of the laser beamwas 177 mm² (beam diameter: 15 mm). The entire sample was then cooled toroom temperature.

(Sample No. 2)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. A ceramic layer comprising porous andpartially stabilized ZrO₂, which had been partially stabilized by 8 wt %of Y₂O₃ as a stabilizer, was then formed to a thickness of 0.5 mm byatmospheric pressure plasma spraying. Then, while cooling the rearsurface of the base material, the top surface of the ceramic layer washeated to 1000° C. by subjecting the top surface of the ceramic layer to30 seconds×800 times of irradiations of a laser beam from a carbondioxide laser. The irradiation area per spot of the laser beam was 177mm² (beam diameter: 15 mmφ). The entire sample was then cooled to roomtemperature.

(Sample No. 3)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. A ceramic layer comprising porous andpartially stabilized ZrO₂, which had been partially stabilized by 8 wt %of Y₂O₃ as a stabilizer, was then formed to a thickness of 0.5 mm byatmospheric pressure plasma spraying. Then, while cooling the rearsurface of the base material, the top surface of the ceramic layer washeated to 1700° C. by subjecting the top surface of the ceramic layer to30 seconds×5 times of irradiations of a laser beam from a carbon dioxidelaser. The irradiation area per spot of the laser beam was 177 mm² (beamdiameter: 15 mmφ). The entire sample was then cooled to roomtemperature.

(Sample No. 4)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. A ceramic layer comprising porous andpartially stabilized ZrO₂, which had been partially stabilized by 10 wt% of Dy₂O₃ as a stabilizer, was then formed to a thickness of 0.5 mm byatmospheric pressure plasma spraying. Then, while cooling the rearsurface of the base material, the top surface of the ceramic layer washeated to 1400° C. by subjecting the top surface of the ceramic layer to30 seconds×100 times of irradiations of a laser beam from a carbondioxide laser. The irradiation area per spot of the laser beam was 177mm² (beam diameter: 15 mmφ). The entire sample was then cooled to roomtemperature.

(Sample No. 5)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. A ceramic layer comprising porous andpartially stabilized ZrO₂, which had been partially stabilized by 10 wt% of Dy₂O₃ as a stabilizer, was then formed to a thickness of 0.5 mm byatmospheric pressure plasma spraying. Then, while cooling the rearsurface of the base material, the top surface of the ceramic layer washeated to 1000° C. by subjecting the top surface of the ceramic layer to30 seconds×800 times of irradiations of a laser beam from a carbondioxide laser. The irradiation area per spot of the laser beam was 177mm² (beam diameter: 15 mmφ). The entire sample was then cooled to roomtemperature.

(Sample No. 6)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. A ceramic layer comprising porous andpartially stabilized ZrO₂, which had been partially stabilized by 10 wt% of Dy₂O₃ as a stabilizer, was then formed to a thickness of 0.5 mm byatmospheric pressure plasma spraying. Then, while cooling the rearsurface of the base material, the top surface of the ceramic layer washeated to 1700° C. by subjecting the top surface of the ceramic layer to30 seconds×5 times of irradiations of a laser beam from a carbon dioxidelaser. The irradiation area per spot of the laser beam was 177 mm² (beamdiameter: 15 mmφ). The entire sample was then cooled to roomtemperature.

(Sample No. 7)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. A ceramic layer comprising porous andpartially stabilized ZrO₂, which had been partially stabilized by 12 wt% of Dy₂O₃ as a stabilizer, was then formed to a thickness of 0.5 mm byatmospheric pressure plasma spraying. Then, while cooling the rearsurface of the base material, the top surface of the ceramic layer washeated to 1400° C. by subjecting the top surface of the ceramic layer to30 seconds×100 times of irradiations of a laser beam from a carbondioxide laser. The irradiation area per spot of the laser beam was 177mm² (beam diameter: 15 mmφ). The entire sample was then cooled to roomtemperature.

(Sample No. 8)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. A ceramic layer comprising porous andpartially stabilized ZrO₂, which had been partially stabilized by 12 wt% of Dy₂O₃ as a stabilizer, was then formed to a thickness of 0.5 mm byatmospheric pressure plasma spraying. Then, while cooling the rearsurface of the base material, the top surface of the ceramic layer washeated to 1000° C. by subjecting the top surface of the ceramic layer to30 seconds×800 times of irradiations of a laser beam from a carbondioxide laser. The irradiation area per spot of the laser beam was 177mm² (beam diameter: 15 mmφ). The entire sample was then cooled to roomtemperature.

(Sample No. 9)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. A ceramic layer comprising porous andpartially stabilized ZrO₂, which had been partially stabilized by 12 wt% of Dy₂O₃ as a stabilizer, was then formed to a thickness of 0.5 mm byatmospheric pressure plasma spraying. Then, while cooling the rearsurface of the base material, the top surface of the ceramic layer washeated to 1700° C. by subjecting the top surface of the ceramic layer to30 seconds×5 times of irradiations of a laser beam from a carbon dioxidelaser. The irradiation area per spot of the laser beam was 177 mm² (beamdiameter: 15 mmφ). The entire sample was then cooled to roomtemperature.

(Sample No. 10)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. A ceramic layer comprising porous andpartially stabilized ZrO₂, which had been partially stabilized by 14 wt% of Yb₂O₃ as a stabilizer, was then formed to a thickness of 0.5 mm byatmospheric pressure plasma spraying. Then, while cooling the rearsurface of the base material, the top surface of the ceramic layer washeated to 1400° C. by subjecting the top surface of the ceramic layer to30 seconds×100 times of irradiations of a laser beam from a carbondioxide laser. The irradiation area per spot of the laser beam was 177mm² (beam diameter: 15 mmφ). The entire sample was then cooled to roomtemperature.

(Sample No. 11)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. A ceramic layer comprising porous andpartially stabilized ZrO₂, which had been partially stabilized by 14 wt% of Yb₂O₃ as a stabilizer, was then formed to a thickness of 0.5 mm byatmospheric pressure plasma spraying. Then, while cooling the rearsurface of the base material, the top surface of the ceramic layer washeated to 1000° C. by subjecting the top surface of the ceramic layer to30 seconds×800 times of irradiations of a laser beam from a carbondioxide laser. The irradiation area per spot of the laser beam was 177mm² (beam diameter: 15 mmφ). The entire sample was then cooled to roomtemperature.

(Sample No. 12)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. A ceramic layer comprising porous andpartially stabilized ZrO₂, which had been partially stabilized by 14 wt% of Yb₂O₃ as a stabilizer, was then formed to a thickness of 0.5 mm byatmospheric pressure plasma spraying. Then, while cooling the rearsurface of the base material, the top surface of the ceramic layer washeated to 1700° C. by subjecting the top surface of the ceramic layer to30 seconds×5 times of irradiations of a laser beam from a carbon dioxidelaser. The irradiation area per spot of the laser beam was 177 mm² (beamdiameter: 15 mmφ). The entire sample was then cooled to roomtemperature.

(Sample No. 13)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. A ceramic layer comprising porous andpartially stabilized ZrO₂, which had been partially stabilized by 16 wt% of Yb₂O₃ as a stabilizer, was then formed to a thickness of 0.5 mm byatmospheric pressure plasma spraying. Then, while cooling the rearsurface of the base material, the top surface of the ceramic layer washeated to 1400° C. by subjecting the top surface of the ceramic layer to30 seconds×100 times of irradiations of a laser beam from a carbondioxide laser. The irradiation area per spot of the laser beam was 177mm² (beam diameter: 15 mmφ). The entire sample was then cooled to roomtemperature.

(Sample No. 14)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. A ceramic layer comprising porous andpartially stabilized ZrO₂, which had been partially stabilized by 16 wt% of Yb₂O₃ as a stabilizer, was then formed to a thickness of 0.5 mm byatmospheric pressure plasma spraying. Then, while cooling the rearsurface of the base material, the top surface of the ceramic layer washeated to 1000° C. by subjecting the top surface of the ceramic layer to30 seconds×800 times of irradiations of a laser beam from a carbondioxide laser. The irradiation area per spot of the laser beam was 177mm² (beam diameter: 15 mmφ). The entire sample was then cooled to roomtemperature.

(Sample No. 15)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. A ceramic layer comprising porous andpartially stabilized ZrO₂, which had been partially stabilized by 16 wt% of Yb₂O₃ as a stabilizer, was then formed to a thickness of 0.5 mm byatmospheric pressure plasma spraying. Then, while cooling the rearsurface of the base material, the top surface of the ceramic layer washeated to 1700° C. by subjecting the top surface of the ceramic layer to30 seconds×5 times of irradiations of a laser beam from a carbon dioxidelaser. The irradiation area per spot of the laser beam was 177 mm² (beamdiameter: 15 mmφ). The entire sample was then cooled to roomtemperature.

Comparative Example 1

For comparison, the following Sample No. 16 was prepared.

(Sample No. 16)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. A ceramic layer comprising porous andpartially stabilized ZrO₂, which had been partially stabilized by 8 wt %of Y₂O₃ as a stabilizer, was then formed to a thickness of 0.5 mm byatmospheric pressure plasma spraying.

The topcoat compositions, thickness, laser irradiation conditions ofSample Nos. 1 to 15, described above, are shown in Table 1.

TABLE 1 Structure of TBC ZrO₂ topcoat Metal binding layer Laserirradiation conditions Stabilizer (CoNiCrAlY) Surface Number of Beammaterial thickness Application thickness Application temperature timesdiameter Sample No. (wt %) (mm) method (mm) method (° C.) (times) (mm)Examples 1 Y₂O₃ (8) 0.5 Atmospheric 0.1 Low pressure 1400 100 15pressure plasma plasma spraying spraying 2 Y₂O₃ (8) 0.5 Atmospheric 0.1Low pressure 1000 800 15 pressure plasma plasma spraying spraying 3 Y₂O₃(8) 0.5 Atmospheric 0.1 Low pressure 1700 5 15 pressure plasma plasmaspraying spraying 4 Dy₂O₃ (10) 0.5 Atmospheric 0.1 Low pressure 1400 10015 pressure plasma plasma spraying spraying 5 Dy₂O₃ (10) 0.5 Atmospheric0.1 Low pressure 1000 800 15 pressure plasma plasma spraying spraying 6Dy₂O₃ (10) 0.5 Atmospheric 0.1 Low pressure 1700 5 15 pressure plasmaplasma spraying spraying 7 Dy₂O₃ (12) 0.5 Atmospheric 0.1 Low pressure1400 100 15 pressure plasma plasma spraying spraying 8 Dy₂O₃ (12) 0.5Atmospheric 0.1 Low pressure 1000 800 15 pressure plasma plasma sprayingspraying 9 Dy₂O₃ (12) 0.5 Atmospheric 0.1 Low pressure 1700 5 15pressure plasma plasma spraying spraying 10 Yb₂O₃ (14) 0.5 Atmospheric0.1 Low pressure 1400 100 15 pressure plasma plasma spraying spraying 11Yb₂O₃ (14) 0.5 Atmospheric 0.1 Low pressure 1000 800 15 pressure plasmaplasma spraying spraying 12 Yb₂O₃ (14) 0.5 Atmospheric 0.1 Low pressure1700 5 15 pressure plasma plasma spraying spraying 13 Yb₂O₃ (16) 0.5Atmospheric 0.1 Low pressure 1400 100 15 pressure plasma plasma sprayingspraying 14 Yb₂O₃ (16) 0.5 Atmospheric 0.1 Low pressure 1000 800 15pressure plasma plasma spraying spraying 15 Yb₂O₃ (16) 0.5 Atmospheric0.1 Low pressure 1700 5 15 pressure plasma plasma spraying sprayingMetal Topcoat Topcoat binding Sample ZrO₂ topcoat thickness applicationlayer No. material (mm) method thickness Metal binding layer applicationmethod Comparative Example 16 ZrO₂ 8 wt % 0.5 Atmospheric 0.1 Lowpressure plasma spraying Y₂O₃ pressure plasma spraying

The gas thermal cycle test device, shown in FIG. 10, was conducted oneach of the above-described Sample Nos. 1 through 16. According to thisdevice, the top surface of a thermal barrier coating film 33 of a testpiece 32 can be heated to approximately 1200° C. or more by a combustiongas burner 31, and the temperature of the interface between the metalbinding layer and the topcoat can be set to 800 to 900° C., which is thetemperature used for an actual gas turbine.

In the durability evaluation test, the surface temperature of thermalbarrier coating film 33 of each sample was heated to 1400° C. Theheating pattern, in which the temperature is raised from roomtemperature to 1400° C. in 5 minutes, held at 1400° C. for 5 minutes,and then stopping the combustion gas to cool for 10 minutes, was set asone cycle. The temperature of a test piece upon cooling was 100° C. orless. This thermal cycle test was conducted and the durability wasevaluated from the number of cycles until peeling of the topcoatoccurred.

The test results are shown in Table 2.

TABLE 2 Number of cycles before peeling occurred Sample No. In thermalcycle test Examples  1 1500 times or more  2 1500 times or more  3 1500times or more  4 1500 times or more  5 1500 times or more  6 1500 timesor more  7 1500 times or more  8 1500 times or more  9 1500 times ormore 10 1500 times or more 11 1500 times or more 12 1500 times or more13 1500 times or more 14 1500 times or more 15 1500 times or moreComparative Example 16 475It is evident in Table 2 that the peeling did not occur with any ofSample Nos. 1 to 15 of the Examples after 1500 thermal cycles. On theother hand, with Sample No. 16 of the Comparative Example, the peelingoccurred at the 475th thermal cycle. It was thus confirmed that thetopcoat of the porous ZrO₂-based ceramic layer having microcracks canbring excellent durability at higher temperatures.

For each of Sample Nos. 1 to 15 of the Examples, the porosity, densityand thermal conductivity of the ceramic layer and the number ofmicrocracks per unit length (1 mm) in the section of the ceramic layerwere examined, and the results are shown in Table 3.

TABLE 3 Thermal Number of Sample Porosity Density conductivitymicrocracks No. (%) (g/mm) (w/(m · K)) (cracks/mm) Examples 1 10 5.0 1.52.3 2 10 5.0 1.5 4.2 3 10 5.0 1.5 1.5 4 10 5.3 1.2 2.8 5 10 5.3 1.2 4.66 10 5.3 1.2 1.3 7 10 5.5 1.2 2.7 8 10 5.5 1.2 4.5 9 10 5.5 1.2 1.4 1010 5.6 1.6 2.0 11 10 5.6 1.6 4.5 12 10 5.6 1.6 1.6 13 10 5.8 1.6 2.2 1410 5.8 1.6 4.2 15 10 5.8 1.6 1.2

EXAMPLES 1 TO 136

Sample Nos. 101 to 136, described below, were prepared.

(Sample No. 101)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. A ZrO₂-10 wt % Dy₂O₃-0.1 wt % Yb₂O₃ layerwas then formed to a thickness of 0.5 mm by atmospheric pressure plasmaspraying.

(Sample No. 102)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. A ZrO₂-10 wt % Dy₂O₃-6 wt % Yb₂O₃ layerwas then formed to a thickness of 0.5 mm by atmospheric pressure plasmaspraying.

(Sample No. 103)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. A ZrO₂-10 wt % Dy₂O₃-10 wt % Yb₂O₃ layerwas then formed to a thickness of 0.5 mm by atmospheric pressure plasmaspraying.

(Sample No. 104)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. A ZrO₂-12 wt % Dy₂O₃-0.1 wt % Yb₂O₃ layerwas then formed to a thickness of 0.5 mm by atmospheric pressure plasmaspraying.

(Sample No. 105)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. A ZrO₂-12 wt % Dy₂O₃-6 wt % Yb₂O₃ layerwas then formed to a thickness of 0.5 mm by atmospheric pressure plasmaspraying.

(Sample No. 106)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. A ZrO₂-12 wt % Dy₂O₃-8 wt % Yb₂O₃ layerwas then formed to a thickness of 0.5 mm by atmospheric pressure plasmaspraying.

(Sample No. 107)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. A ZrO₂-14 wt % Dy₂O₃-0.1 wt % Yb₂O₃ layerwas then formed to a thickness of 0.5 mm by atmospheric pressure plasmaspraying.

(Sample No. 108)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. A ZrO₂-14 wt % Dy₂O₃-4 wt % Yb₂O₃ layerwas then formed to a thickness of 0.5 mm by atmospheric pressure plasmaspraying.

(Sample No. 109)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. A ZrO₂-14 wt % Dy₂O₃-6 wt % Yb₂O₃ layerwas then formed to a thickness of 0.5 mm by atmospheric pressure plasmaspraying.

(Sample No. 110)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. A ZrO₂-0.1 wt % Dy₂O₃-12 wt % Yb₂O₃ layerwas then formed to a thickness of 0.5 mm by atmospheric pressure plasmaspraying.

(Sample No. 111)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. A ZrO₂-6 wt % Dy₂O₃-12 wt % Yb₂O₃ layerwas then formed to a thickness of 0.5 mm by atmospheric pressure plasmaspraying.

(Sample No. 112)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. A ZrO₂-8 wt % Dy₂O₃-12 wt % Yb₂O₃ layerwas then formed to a thickness of 0.5 mm by atmospheric pressure plasmaspraying.

(Sample No. 113)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. A ZrO₂-0.1 wt % Dy₂O₃-14 wt % Yb₂O₃ layerwas then formed to a thickness of 0.5 mm by atmospheric pressure plasmaspraying.

(Sample No. 114)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. A ZrO₂-4 wt % Dy₂O₃-14 wt % Yb₂O₃ layerwas then formed to a thickness of 0.5 mm by atmospheric pressure plasmaspraying.

(Sample No. 115)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. A ZrO₂-6 wt % Dy₂O₃-14 wt % Yb₂O₃ layerwas then formed to a thickness of 0.5 mm by atmospheric pressure plasmaspraying.

(Sample No. 116)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. A ZrO₂-0.1 wt % Dy₂O₃-16 wt % Yb₂O₃ layerwas then formed to a thickness of 0.5 mm by atmospheric pressure plasmaspraying.

(Sample No. 117)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. A ZrO₂-2 wt % Dy₂O₃-16 wt % Yb₂O₃ layerwas then formed to a thickness of 0.5 mm by atmospheric pressure plasmaspraying.

(Sample No. 118)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. A ZrO₂-4 wt % Dy₂O₃-16 wt % Yb₂O₃ layerwas then formed to a thickness of 0.5 mm by atmospheric pressure plasmaspraying.

(Sample No. 119)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. After the CoNiCrAlY alloy layer wassurface-polished to be suitable for an electron beam physical vapordeposition, a ZrO₂-10 wt % Dy₂O₃-0.1 wt % Yb₂O₃ layer was formed to athickness of 0.5 mm by the electron beam physical vapor deposition.

(Sample No. 120)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. After the CoNiCrAlY alloy layer wassurface-polished to be suitable for an electron beam physical vapordeposition, a ZrO₂-10 wt % Dy₂O₃-6 wt % Yb₂O₃ layer was formed to athickness of 0.5 mm by the electron beam physical vapor deposition.

(Sample No. 121)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. After the CoNiCrAlY alloy layer wassurface-polished to be suitable for an electron beam physical vapordeposition, a ZrO₂-10 wt % Dy₂O₃-10 wt % Yb₂O₃ layer was formed to athickness of 0.5 mm by the electron beam physical vapor deposition.

(Sample No. 122)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. After the CoNiCrAlY alloy layer wassurface-polished to be suitable for an electron beam physical vapordeposition, a ZrO₂-12 wt % Dy₂O₃-0.1 wt % Yb₂O₃ layer was formed to athickness of 0.5 mm by the electron beam physical vapor deposition.

(Sample No. 123)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. After the CoNiCrAlY alloy layer wassurface-polished to be suitable for an electron beam physical vapordeposition, a ZrO₂-12 wt % Dy₂O₃-6 wt % Yb₂O₃ layer was formed to athickness of 0.5 mm by the electron beam physical vapor deposition.

(Sample No. 124)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. After the CoNiCrAlY alloy layer wassurface-polished to be suitable for an electron beam physical vapordeposition, a ZrO₂-12 wt % Dy₂O₃-8 wt % Yb₂O₃ layer was formed to athickness of 0.5 mm by the electron beam physical vapor deposition.

(Sample No. 125)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. After the CoNiCrAlY alloy layer wassurface-polished to be suitable for an electron beam physical vapordeposition, a ZrO₂-14 wt % Dy₂O₃-0.1 wt % Yb₂O₃ layer was formed to athickness of 0.5 mm by the electron beam physical vapor deposition.

(Sample No. 126)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. After the CoNiCrAlY alloy layer wassurface-polished to be suitable for an electron beam physical vapordeposition, a ZrO₂-14 wt % Dy₂O₃-4 wt % Yb₂O₃ layer was formed to athickness of 0.5 mm by the electron beam physical vapor deposition.

(Sample No. 127)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. After the CoNiCrAlY alloy layer wassurface-polished to be suitable for an electron beam physical vapordeposition, a ZrO₂-14 wt % Dy₂O₃-6 wt % Yb₂O₃ layer was formed to athickness of 0.5 mm by the electron beam physical vapor deposition.

(Sample No. 128)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. After the CoNiCrAlY alloy layer wassurface-polished to be suitable for an electron beam physical vapordeposition, a ZrO₂-0.1 wt % Dy₂O₃-12 wt % Yb₂O₃ layer was formed to athickness of 0.5 mm by the electron beam physical vapor deposition.

(Sample No. 129)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. After the CoNiCrAlY alloy layer wassurface-polished to be suitable for an electron beam physical vapordeposition, a ZrO₂-6 wt % Dy₂O₃-12 wt % Yb₂O₃ layer was formed to athickness of 0.5 mm by the electron beam physical vapor deposition.

(Sample No. 130)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. After the CoNiCrAlY alloy layer wassurface-polished to be suitable for an electron beam physical vapordeposition, a ZrO₂-8 wt % Dy₂O₃-12 wt % Yb₂O₃ layer was formed to athickness of 0.5 mm by the electron beam physical vapor deposition.

(Sample No. 131)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. After the CoNiCrAlY alloy layer wassurface-polished to be suitable for an electron beam physical vapordeposition, a ZrO₂-0.1 wt % Dy₂O₃-14 wt % Yb₂O₃ layer was formed to athickness of 0.5 mm by the electron beam physical vapor deposition.

(Sample No. 132)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. After the CoNiCrAlY alloy layer wassurface-polished to be suitable for an electron beam physical vapordeposition, a ZrO₂-4 wt % Dy₂O₃-14 wt % Yb₂O₃ layer was formed to athickness of 0.5 mm by the electron beam physical vapor deposition.

(Sample No. 133)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. After the CoNiCrAlY alloy layer wassurface-polished to be suitable for an electron beam physical vapordeposition, a ZrO₂-6 wt % Dy₂O₃-14 wt % Yb₂O₃ layer was formed to athickness of 0.5 mm by the electron beam physical vapor deposition.

(Sample No. 134)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. After the CoNiCrAlY alloy layer wassurface-polished to be suitable for an electron beam physical vapordeposition, a ZrO₂-0.1 wt % Dy₂O₃-16 wt % Yb₂O₃ layer was formed to athickness of 0.5 mm by the electron beam physical vapor deposition.

(Sample No. 135)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. After the CoNiCrAlY alloy layer wassurface-polished to be suitable for an electron beam physical vapordeposition, a ZrO₂-2 wt % Dy₂O₃-16 wt % Yb₂O₃ layer was formed to athickness of 0.5 mm by the electron beam physical vapor deposition.

(Sample No. 136)

The top surface of the base material was grid-blasted with Al₂O₃ grainsand put in a state suitable for low pressure plasma spraying. ACoNiCrAlY alloy layer was then formed to a thickness of 0.1 mm by thelow pressure plasma spraying. After the CoNiCrAlY alloy layer wassurface-polished to be suitable for an electron beam physical vapordeposition, a ZrO₂-4 wt % Dy₂O₃-16 wt % Yb₂O₃ layer was formed to athickness of 0.5 mm by the electron beam physical vapor deposition.

Comparative Example 101

For comparison, the following Sample No. 137 was prepared.

(Sample No. 137)

A CoNiCrAlY alloy layer was formed to a thickness of 0.1 mm on the basematerial by low pressure plasma spraying. A ZrO₂-8 wt % Y₂O₃ layer wasthen formed to a thickness of 0.5 mm by atmospheric pressure plasmaspraying.

Each of the Sample Nos. 101 to 137 was heated at 850° C. under vacuumfor 24 hours after the film formation.

The topcoat compositions, lamination methods and thickness of SampleNos. 101 to 137, described above, are shown in Table 4.

TABLE 4 Structure of TBC ZrO₂ topcoat Material (amount of stabilizeradded to ZrO₂) Total Metal binding layer Added Added added (CoNiCrAlY)amount of amount of amount thickness thickness Application Sample No.Dy₂O₃ (wt %) Yb₂O₃ (wt %) (wt %) (mm) Application method (mm) methodExamples 101 10 0.1 10.1 0.5 Atmospheric pressure 0.1 Low pressureplasma spraying plasma spraying 102 10 6 16 0.5 Atmospheric pressure 0.1Low pressure plasma spraying plasma spraying 103 10 10 20 0.5Atmospheric pressure 0.1 Low pressure plasma spraying plasma spraying104 12 0.1 12.1 0.5 Atmospheric pressure 0.1 Low pressure plasmaspraying plasma spraying 105 12 6 18 0.5 Atmospheric pressure 0.1 Lowpressure plasma spraying plasma spraying 106 12 8 20 0.5 Atmosphericpressure 0.1 Low pressure plasma spraying plasma spraying 107 14 0.114.1 0.5 Atmospheric pressure 0.1 Low pressure plasma spraying plasmaspraying 108 14 4 18 0.5 Atmospheric pressure 0.1 Low pressure plasmaspraying plasma spraying 109 14 6 20 0.5 Atmospheric pressure 0.1 Lowpressure plasma spraying plasma spraying 110 0.1 12 12.1 0.5 Atmosphericpressure 0.1 Low pressure plasma spraying plasma spraying 111 6 12 180.5 Atmospheric pressure 0.1 Low pressure plasma spraying plasmaspraying 112 8 12 20 0.5 Atmospheric pressure 0.1 Low pressure plasmaspraying plasma spraying 113 0.1 14 14.1 0.5 Atmospheric pressure 0.1Low pressure plasma spraying plasma spraying 114 4 14 18 0.5 Atmosphericpressure 0.1 Low pressure plasma spraying plasma spraying 115 6 14 200.5 Atmospheric pressure 0.1 Low pressure plasma spraying plasmaspraying 116 0.1 16 16.1 0.5 Atmospheric pressure 0.1 Low pressureplasma spraying plasma spraying 117 2 16 18 0.5 Atmospheric pressure 0.1Low pressure plasma spraying plasma spraying 118 4 16 20 0.5 Atmosphericpressure 0.1 Low pressure plasma spraying plasma spraying 119 10 0.110.1 0.5 Electron beam 0.1 Low pressure physical vapor plasma sprayingdeposition 120 10 6 16 0.5 Electron beam 0.1 Low pressure physical vaporplasma spraying deposition 121 10 10 20 0.5 Electron beam 0.1 Lowpressure physical vapor plasma spraying deposition 122 12 0.1 12.1 0.5Electron beam 0.1 Low pressure physical vapor plasma spraying deposition123 12 6 18 0.5 Electron beam 0.1 Low pressure physical vapor plasmaspraying deposition 124 12 8 20 0.5 Electron beam 0.1 Low pressurephysical vapor plasma spraying deposition 125 14 0.1 14.1 0.5 Electronbeam 0.1 Low pressure physical vapor plasma spraying deposition 126 14 418 0.5 Electron beam 0.1 Low pressure physical vapor plasma sprayingdeposition 127 14 6 20 0.5 Electron beam 0.1 Low pressure physical vaporplasma spraying deposition 128 0.1 12 12.1 0.5 Electron beam 0.1 Lowpressure physical vapor plasma spraying deposition 129 6 12 18 0.5Electron beam 0.1 Low pressure physical vapor plasma spraying deposition130 8 12 20 0.5 Electron beam 0.1 Low pressure physical vapor plasmaspraying deposition 131 0.1 14 14.1 0.5 Electron beam 0.1 Low pressurephysical vapor plasma spraying deposition 132 4 14 18 0.5 Electron beam0.1 Low pressure physical vapor plasma spraying deposition 133 6 14 200.5 Electron beam 0.1 Low pressure physical vapor plasma sprayingdeposition 134 0.1 16 16.1 0.5 Electron beam 0.1 Low pressure physicalvapor plasma spraying deposition 135 2 16 18 0.5 Electron beam 0.1 Lowpressure physical vapor plasma spraying deposition 136 4 16 20 0.5Electron beam 0.1 Low pressure physical vapor plasma spraying depositionMetal binding Topcoat layer Metal binding Sample thickness Topcoatapplication thickness layer application No. ZrO₂ topcoat material (mm)method (mm) method Comp. ex. 137 ZrO₂ · 8 wt % Y₂O₃ 0.5 Atmosphericpressure 0.1 Low pressure plasma spraying plasma spraying

Next, a durability evaluation test by the combustion gas thermal cycletest device, shown in FIG. 10, was conducted on each of the Sample Nos.101 to 137. According to this device, the top surface of a thermalbarrier coating film 33 of a test piece 32 can be heated toapproximately 1200° C. or more by a combustion gas burner 31, and thetemperature of the interface between the metal binding layer and thetopcoat can be set to 800 to 900° C., which is the temperature of anactual gas turbine.

In the durability evaluation test, the surface of the thermal barriercoating film 33 of each Sample was heated to 1400° C. and thetemperature of the interface between the metal binding layer and thetopcoat of the thermal barrier coating film 33 was set to 900° C. Theheating pattern, in which the temperature is raised from roomtemperature to 1400° C. in 5 minutes, held at 1400° C. for 5 minutes,and then stopping the combustion gas to cool for 10 minutes, was set asone cycle. The temperature of a test piece upon cooling was 100° C. orless. This thermal cycle test was conducted and the durability wasevaluated from the number of cycles until peeling of the topcoatoccurred.

The test results are shown in Table 5.

TABLE 5 Number of cycles before peeling occurred Sample No. in thermalcycle test Examples 101 1500 times or more 102 1500 times or more 1031500 times or more 104 1500 times or more 105 1500 times or more 1061500 times or more 107 1500 times or more 108 1500 times or more 1091500 times or more 110 1500 times or more 111 1500 times or more 1121500 times or more 113 1500 times or more 114 1500 times or more 1151500 times or more 116 1500 times or more 117 1500 times or more 1181500 times or more 119 1500 times or more 120 1500 times or more 1211500 times or more 122 1500 times or more 123 1500 times or more 1241500 times or more 125 1500 times or more 126 1500 times or more 1271500 times or more 128 1500 times or more 129 1500 times or more 1301500 times or more 131 1500 times or more 132 1500 times or more 1331500 times or more 134 1500 times or more 135 1500 times or more 1361500 times or more Comparative example 137 475

It is evident in Table 5 that the peeling did not occur with any ofSample Nos. 101 to 136 of the Examples after 1500 thermal cycles. On theother hand, with Sample No. 137 of the Comparative Example, the peelingoccurred at the 475th thermal cycle. It was thus confirmed that thetopcoat of the ZrO₂—(Dy₂O₃+Yb₂O₃) layer brings excellent durability athigher temperatures.

INDUSTRIAL APPLICABILITY

According to the thermal barrier coating material for the first aspectof the invention, since the topcoat is of the ceramic layer comprisingpartially stabilized ZrO₂ which is porous and yet has microcracks thatextend in the thickness direction, both the high thermal barrier effectcomparable to those of conventional porous thermal barrier coatings andthe high peeling resistance comparable to thermal barrier coatings whichcan be obtained by the electron beam physical vapor deposition can beobtained. The thermal barrier coating material which provides anadequate durability even in environments of higher temperatures thanthose of conventional temperatures can thus be obtained.

According to the method for producing the thermal barrier coatingmaterial for the first aspect of the invention, since the longitudinalmicrocracks are formed in the ceramic layer by pulse irradiation of thelaser beam after lamination of the ceramic layer, the thermal barriercoating material can be formed extremely simply and at low cost. Thismethod may also be applied selectively to only the thermally severeparts of the gas turbine member and the like.

According to the gas turbine member for the first aspect of theinvention, since the topcoat of the thermal barrier coating film is of aceramic layer comprising a partially stabilized ZrO₂ which is porous andyet has microcracks that extend in the thickness direction, and the gasturbine member is covered with this thermal barrier coating film, thegas turbine member which provides an adequate durability even inenvironments of higher temperature than those of conventionaltemperatures can be obtained. Although the CO₂ gas laser was used as amethod of introducing longitudinal microcracks, a plasma flame, a YAGlaser, an electron beam or other heating source may obviously be usedinstead.

According to the gas turbine for the first aspect of the invention, theapplication of the coating of high durability and high thermal barrierproperty can bring an increase of the turbine entrance temperature ofthe gas turbine and a decrease of the amount of cooling air so that thethermal efficiency of the gas turbine is improved. When the coating isapplied to an existing gas turbine, the lifetime of high-temperatureparts can be elongated further because of the high thermal barriereffect and durability of the thermal barrier coating.

According to the thermal barrier coating material for the second aspectof the invention, since the topcoat is of a composite material of DySZand YbSZ, DySZ being higher in thermal barrier effect than YSZ, andYbSZ, being higher in peeling resistance than YSZ, the thermal barriereffect and the peeling resistance which are higher in comparison tothose of the prior art can be obtained. The thermal barrier coatingmaterial which provides an adequate durability even in environments ofhigher temperature than those of conventional temperatures can thus beobtained.

According to the gas turbine member for the second aspect of theinvention, since the topcoat of the thermal barrier coating film is ofthe composite material of DySZ and YbSZ, DySZ being higher in thermalbarrier effect than YSZ, and YbSZ being higher in peeling resistancethan YSZ, and the gas turbine member is covered with this thermalbarrier coating film, the gas turbine member which provides an adequatedurability even in environments of higher temperature than those ofconventional temperatures can be obtained.

According to the gas turbine for the second aspect of the invention, theapplication of the coating of high durability and high thermal barrierproperty can bring an increase of the turbine entrance temperature ofthe gas turbine and a decrease of the amount of cooling air so that thethermal efficiency of the gas turbine is improved. When the coating isapplied to an existing gas turbine, the lifetime of high-temperatureparts can be elongated further because of the high thermal barriereffect and durability of the thermal barrier coating.

According to the gas turbine member for the third aspect of theinvention, since the topcoat is of the ZrO₂-rare earth oxide layerproduced by thermal spraying of the TBC thermal spraying raw materialwhich is obtained by mixing zirconia having a specific surface area ofat least 10 m²/g and a rare earth oxide having a specific surface areaof at least 10 m²/g, the stabilized zirconia layer which is higher instability than the prior art is obtained. The gas turbine member whichprovides an adequate durability even in environments of highertemperature than those of conventional temperatures can thus beprovided.

According to the gas turbine for the third aspect of the invention, theapplication of the coating of high durability and high thermal barrierproperty can bring an increase of the turbine entrance temperature ofthe gas turbine and a decrease of the amount of cooling air so that thethermal efficiency of the gas turbine is improved. When the coating isapplied to an existing gas turbine, the lifetime of high-temperatureparts can be elongated further because of the high thermal barriereffect and durability of the thermal barrier coating.

1. A thermal barrier coating material, comprising a metal binding layerlaminated on a base material and a ceramic layer laminated on the metalbinding layer, the ceramic layer comprising partially stabilized ZrO₂which is partially stabilized by additives of Dy₂O₃ and Yb₂O₃, whereinthe ceramic layer is porous and has a porosity which ranges from 10 to30%, and wherein said ceramic layer is a film produced by thermalspraying of a ZrO₂—Dy₂O₃—Yb₂O₃ powder which has been obtained from asolid solution of a mixture of ZrO₂, Dy₂O₃ and Yb₂O₃ powders, whereineach powder used to form said mixture has a specific surface area of atleast 10 m²/g.
 2. The thermal barrier coating material according toclaim 1, wherein said Dy₂O₃ is in a range of 0.01 wt % to 16.00 wt %,said Yb₂O₃ is in a range of 0.01 wt % to 17.00 wt %, a sum of said Dy₂O₃and said Yb₂O₃ is in a range of 10 wt % to 20 wt %.
 3. The thermalbarrier coating material according to claim 2, wherein said Dy₂O₃ is ina range of 0.1 wt % to 4 wt %.
 4. The thermal barrier coating materialaccording to claim 2, wherein said Dy₂O₃ is in a range of 0.1 wt % to 2wt %.
 5. A gas turbine member, comprising the thermal barrier coatingmaterial according to claim
 1. 6. A gas turbine, comprising the gasturbine member according to claim
 5. 7. The thermal barrier coatingmaterial according to claim 1, wherein said ZrO₂ excluding stabilizersis in a range of 80 wt % to 90 wt %.
 8. The thermal barrier coatingmaterial according to claim 1, wherein said ceramic layer consists ofpartially stabilized ZrO₂ which is partially stabilized only byadditives of Dy₂O₃ and Yb₂O₃.
 9. The thermal barrier coating materialaccording to claim 1, wherein a density of a porous portion of saidceramic layer is in a range of 4 g/mm³ to 6.5 g/mm³.
 10. The thermalbarrier coating material according claim 9, wherein a thermalconductivity of said ceramic layer is in a range of 0.5 w/m·K to 5w/m·K.
 11. The thermal barrier coating material according claim 1,wherein a thermal conductivity of said ceramic layer is in a range of0.5 w/m·K to 5 w/m·K.
 12. The thermal barrier coating material accordingto claim 1, wherein the ceramic layer has microcracks that extend in athickness direction of the ceramic layer, and the number of saidmicrocracks per unit length (1 mm) on a section of said ceramic layer isin a range of 1 to
 10. 13. The thermal barrier coating materialaccording to claim 1, wherein the ceramic layer has a thickness of 0.05mm to 1.5 mm.
 14. The thermal barrier coating material according toclaim 1, wherein the ceramic layer has a thickness of 0.1 mm to 1.5 mm.15. The thermal barrier coating material according to claim 1, whereinsaid mixture is mixed with a binder or dispersant so as to form aslurry, the slurry is granulated to form particles having a meanparticle diameter of 10 to 100 μm, and then the particles are heated at1300 to 1600° C. for 1 to 10 hours.